Within recent years, particularly since the development of methods for the intensive treatment of syphilis, aneurysms of the large vessels, on the whole, have not been of as much clinical interest to physicians and students as formerly. Recently a patient with aneurysm of the innominate artery was under my observation. This case perhaps illustrates the potential danger to the patient of vigorous antisyphilitic treatment in association with aneurysm, with its resultant subjective improvement, and also may serve as a gentle reminder that clinicians in the past were thoroughly familiar with aneurysm of this type, that they developed methods of treating such an aneurysm which often were successful and that past experience may well serve as a guide toward improving in the future the methods of treatment when an aneurysm involves this particular vessel. Curiously, aneurysms of the innominate artery are by no means common. According to Osler1 and Reid